Ion-exchange resins are conventionally widely used for treating liquid for ion-exchanging and/or adsorption. However, since most of the ion-exchange groups are located in the inner portion of the resin rather than in the surface area thereof, this treatment has drawbacks in that the reaction rate is low and so the treatment is time-consuming, and it is also difficult to conduct ion-exchanging and/or adsorption with high efficiency. If the ion-exchange resins are powdered or finely grained, other drawbacks are brought about that their handling becomes troublesome and the liquid-flow resistance becomes very high. It was proposed recently to treat a liquid with an ion-exchange fiber having a large surface area, so as to attain high reaction rate and high freedom in the selection of the form of the ion-exchanger in use. However, this method has a lethal drawback in its low treatment capacity due to the voluminousness of the fiber.
The present inventors intensively researched to eliminate the above-mentioned drawbacks to complete the present invention.